If the sores, itching, pain, and sheer shame of sexually transmitted infections (STIs) don't provide enough reasons for people to have safe sex, how about cash rewards? That's what a group of MIT researchers asked in Tanzania, Co.Exist reports.

More than 5% of adults in Tanzania live with HIV. Given the stigma many Tanzanians associate with HIV, the researchers decided to study the transmission of STIs (chlamydia, gonorrhea, trichomonas, and M. genitalium) as a stand-in.